Prostheses for implantation in blood vessels or other similar organs of the living body are, in general, well known in the medical art. For example, prosthetic vascular grafts constructed of biocompatible materials, such as Dacron or expanded, porous polytetrafluoroethylene (PTFE) tubing, have been employed to replace or bypass damaged or occluded natural blood vessels. In general, endovascular grafts typically include a graft anchoring component that operates to hold the tubular graft in its intended position within the blood vessel. Most commonly, the graft anchoring component is one or more radially compressible stents that are radially expanded in situ to anchor the tubular graft to the wall of a blood vessel or anatomical conduit. Thus, endovascular grafts are typically held in place by mechanical engagement and friction due to the opposition forces provided by the expandable stents.
In general, rather than performing an open surgical procedure to implant a graft that may be traumatic and invasive, stent grafts are preferably deployed through a less invasive intraluminal delivery. More particularly, a lumen of the vasculature is accessed at a convenient and low trauma entry point, and the compressed stent graft is routed through the vasculature to the site where the prosthesis is to be deployed. Intraluminal deployment of the self expanding device is typically effected using a delivery catheter with coaxial inner and outer tubes arranged for relative axial movement. For example, a self-expanding stent graft may be compressed and disposed within the distal end of an outer catheter tube distal of a stop fixed to the inner member. The catheter is then routed though a body lumen until the end of the catheter containing the stent graft is positioned at the intended treatment site. The stop on the inner member is then held stationary while the outer tube of the delivery catheter is withdrawn. The stop prevents the stent graft from being withdrawn with the sheath. As the sheath is withdrawn, the stent graft is released from the confines of the sheath and radially self-expands so that at least a portion of it contacts and substantially conforms to a portion of the surrounding interior wall of the lumen, e.g., the blood vessel wall or anatomical conduit.
Grafting procedures are also known for treating aneurysms. Aneurysms result from weak, thinned blood vessel walls that “balloon” or expand due to aging, disease and/or blood pressure in the vessel. Consequently, aneurysmal vessels have a potential to rupture, causing internal bleeding and potentially life threatening conditions. Grafts are often used to isolate aneurysms or other blood vessel abnormalities from normal blood pressure, reducing pressure on the weakened vessel wall and reducing the chance of vessel rupture. As such, a tubular endovascular graft may be placed within the aneurysmal blood vessel to create an artificial flow conduit through the aneurysm, thereby reducing if not nearly eliminating the exertion of blood pressure on the aneurysm.
While aneurysms can occur in any blood vessel, most occur in the aorta and peripheral arteries. Depending on the region of the aorta involved, the aneurysm may extend into areas having vessel bifurcations or segments of the aorta from which smaller “branch” arteries extend. Various types of aortic aneurysms may be classified on the basis of the region of aneurysmal involvement. For example, thoracic aortic aneurysms include aneurysms present in the ascending thoracic aorta, the aortic arch, and branch arteries that emanate therefrom, such as subclavian arteries, and also include aneurysms present in the descending thoracic aorta and branch arteries that emanate therefrom, such as thoracic intercostal arteries and/or the suprarenal abdominal aorta and branch arteries that emanate therefrom, such as renal, superior mesenteric, celiac and/or intercostal arteries. Lastly, abdominal aortic aneurysms include aneurysms present in the aorta below the diaphragm, e.g., pararenal aorta and the branch arteries that emanate therefrom, such as the renal arteries.
Unfortunately, not all patients diagnosed with aortic aneurysms are presently considered to be candidates for endovascular grafting. This is largely due to the fact that most of the endovascular grafting systems of the prior art are not designed for use in regions of the aorta from which side branches extend. The deployment of endovascular grafts within regions of the aorta from which branch arteries extend presents additional technical challenges because, in those cases, the endovascular graft must be designed, implanted, and maintained in a manner which does not impair the flow of blood into the branch arteries.
To accommodate side branches, a main vessel stent graft having a fenestration or opening in a side wall thereof is often utilized. The fenestration is positioned to align with the ostium of the branch vessel after deployment. In use, the proximal end of the graft having one or more side openings is securely anchored in place, and the fenestrations or openings are configured and deployed to avoid blocking or restricting blood flow into the side branches. Fenestrations alone do not form discrete conduit(s) through which blood is channeled into each side branch artery. As a result, the edges of the graft surrounding the fenestrations are prone to: i) the leakage of blood into the space between the outer surface of the aortic graft and the surrounding aortic wall; or ii) post-implantation migration or movement of the stent graft causing misalignment of the fenestration(s) and the branch artery(ies), which may result in impaired flow into the branch artery(ies).
In some cases, another stent graft, often referred to as a branch graft, may then be deployed through the fenestration into the branch vessel to provide a conduit for blood flow to the branch vessel. The branch graft is preferably sealingly connected to the main graft in situ to prevent undesired leakage.
An especially challenging area to deploy and seal branch grafts is the aortic arch. In a significant population of patients with thoracic aortic aneurysms (TAA), there is no healthy vessel tissue for fixation and sealing of stent grafts distal to the branches of the aortic arch. Thus, a stent graft deployed in the aortic arch spans across one or more branch arteries.
Thus, there remains a need in the art for improvements for directing flow from fenestrations to the corresponding branch vessels. Embodiments hereof relate to a side branch prosthesis having a mobile and resilient sealing assembly to provide a blood tight seal between the side branch vessel prosthesis and a prosthesis implanted within a main vessel. The sealing assembly may be utilized in conjunction with pre-fenestrated grafts or grafts having fenestrations created in situ.